In recent years, a white LED device has come into practice and attracted attention because they would be expected to replace fluorescent lamps. The development of an LED chip which employs a gallium nitride (GaN)-based compound semiconductor and emits light in blue to ultraviolet regions has spurred the commercialization of the white LED device.
There are mainly two methods for obtaining white light by using the LED chip which emits light in blue to ultraviolet regions (see, for example, Non-Patent Document 1). In a first method, white light is obtained from blue light which is radiated by a blue LED chip and yellow light which is obtained by exciting a fluorescent material (cerium-doped yttrium aluminum garnet (YAG:Ce), etc.) using the blue light. In a second method, white light is obtained by exciting a plurality of fluorescent materials using light which is radiated by an LED chip which emits light in a violet region to an ultraviolet region to obtain red, green, and blue (three primary colors) light. Fluorescent materials includes Y2O2S:Eu (abbreviated as P22-RE3) for red, ZnS:Cu, Al (abbreviated as P22-GN4) or (Ba, Mg)Al10O17:Eu, Mn (abbreviated as LP-G3) for green, and (Sr,Ca,Ba,Mg)10(PO4)6Cl2:Eu (abbreviated as LP-B1) or (Ba,Mg)Al10O7:Eu (abbreviated as LP-B4) for blue.
The white LED device is achieved by packaging the LED chip which emits light in blue to ultraviolet regions and the fluorescent material using a sealing resin material. The package is formed of a sealing resin material which is shaped into a bullet (see, for example, Non-Patent Document 2).
Hereinafter, the conventional white LED device having the bullet-shaped package will be described with reference to FIG. 45.
As shown in FIG. 45, in the conventional white LED device 100, an LED chip 102 which emits light in blue to ultraviolet regions is fixed via a chip fixing paste material 103, such as a Ag paste material, an insulating paste material or the like, to a bottom surface of a cup-shaped die pad portion provided at one end of a first lead frame 101A.
A first electrode 104A and a second electrode 104B are formed on an upper surface of the LED chip 102. The first electrode 104A is electrically connected via a first wire 105A to the first lead frame 101A, and the second electrode 104B is electrically connected via a second wire 105B to a second lead frame 100B which is paired with the first lead frame 101A.
The LED chip 102 is sealed by a resin material 105 which is molded in the shape of a bullet. The resin material 105 is generally a resin material transparent to visual light, such as an epoxy resin, a silicone resin or the like. Also, a fluorescent material 106, such as those described above, is kneaded into the resin material 105 (see, for example, Patent Document 1).
Non-Patent Document 1; Kazuyuki Tadatomo et al., “Mitsubishi Cable Industries Review”, Vol. 99, July 2002, pp. 35-41
Non-Patent Document 2: Masaru Sugimoto et al., “Matsushita Electric Works Technical Report”, Vol. 53, No. 1, pp. 4-9
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-71908
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-93724